Copper Fiber Research Articles

A Multi-Scale Simulation Approach to Investigate Local Contact Temperatures for Commercial Cu-Full and Cu-Free Brake Pads

Copper from vehicles disc brakes is one main contributor of the total copper found in the environment. Therefore, the U.S. Environmental Protection Agency (EPA) and the automotive industries started the Copper-Free Brake Initiative. The pad friction material is essentially composed of a binder, fillers, reinforcing fibres and frictional additives. Copper and brass fibres are the most commonly used fibres in brake pads. There is a need to understand how the contact temperature distribution will change if copper-based fibres are changed to steel fibres. The aim of this work is, therefore, to investigate how this change could influence the local contact temperatures. This is done by developing a multi-scale simulation approach which combines cellular automaton, finite element analysis (FEA) and computational fluid dynamics (CFD) approaches with outputs from inertia brake dyno bench tests of Cu-full and Cu-free pads. FEA and thermal-CFD are used to set the pressure and the temperature boundary conditions of the cellular automaton. The outputs of dyno tests are used to calibrate FEA and CFD simulations. The results of the study show lower peaks in contact temperature and a more uniform temperature distribution for the Cu-free pad friction material.

Preparing a novel gradient porous metal fiber sintered felt with better manufacturability for hydrogen production via methanol steam reforming

The porous copper fiber sintered felts with gradient porosity structure (gradient PCFSFs) as catalyst supports is beneficial for heat and mass transfer for methanol steam reforming (MSR). However, the previously developed gradient PCFSF based on the velocity distribution introduces curved interface between different porosity portions, making the mold pressing method for its preparation more sensitive to tiny process changes. To improve its manufacturability, a novel gradient PCFSF with planar interface (PCFSF-SLR) is proposed in this paper by fabrication with multi-step mold pressing and solid phase sintering method using cutting copper fibers. Furthermore, MSR experiments under different gas hourly space velocities and reaction temperatures are conducted to verify the characteristics of PCFSF-SLR loaded with Cu/Zn/Al/Zr catalyst. The results have shown that the reaction characteristics of the PCFSF-SLR were similar to those with curved interfaces, and PCFSF-SLRs with a middle portion porosity of 0.9 have better hydrogen production performance and lower carbon monoxide concentration. More importantly, the results indicated that the methanol conversion and hydrogen flow rate of the gradient PCFSF with planar interface and porosity of 0.7-0.9-0.8 were close or even almost the same with that of the best gradient PCFSFs with curved interface and porosities of 0.7-0.9-0.8 and 0.8-0.9-0.7. Therefore, the proposed PCFSF-SLR provides a superior alternative to gradient PCFSFs with better manufacturability.

Mechanical characteristics of wood, ceramic, metal and carbon fiber-based PLA composites fabricated by FDM

Fused deposition modeling (FDM) has gained much attention in recent years, as it revolutionizes the rapid manufacturing of customized polymer-based composite components. To facilitate the engineering applications of these FDM-printed components, understanding their basic mechanical behaviors is necessary. In this paper, the mechanical characteristics, including tensile and flexural properties of samples fabricated by FDM with different additives, i.e. wood, ceramic, copper, aluminum and carbon fiber, based polylactic acid (PLA) composites are comprehensively investigated. The effects of different PLA composites, build orientations and raster angles on mechanical responses are compared and analyzed in detail. It is found that ceramic, copper and aluminum-based PLA composite parts have similar or even increased mechanical properties compared with virgin PLA made parts. In most cases, PLA composite samples that are FDM-printed in on-edge orientation with +45°/−45° raster angles have the highest mechanical strength and modulus. It is worth noting that the results in this research provide a useful guideline for fabricating complex functional PLA composite components with optimized mechanical properties.

Fabrication and Uniaxial Tensile Properties of Soldered Porous Copper Fiber-Sintered Sheets

Porous copper fiber-sintered sheets (PCFSSs) with different porosities were fabricated through the solid-phase sintering method using cutting copper fibers. PCFSSs with the same porosity and different porosities were then joined via a fluxless soldering method. By analyzing the uniaxial tensile property of the PCFSSs, the formation mechanism of the soldered PCFSSs was investigated. The difference in the tensile properties between the soldered and original PCFSSs was examined. Experimental results indicated that, for the PCFSSs with homogeneous porosity, reducing the porosity increased the tensile strength and elongation at break significantly. The fluxless soldering method with the lead-free solder resulted in excellent joining of the PCFSSs with the same porosity and different porosities. Moreover, the final tensile strength of the soldered PCFSSs with the same porosity was nearly equal to that of their parent PCFSSs. The tensile strength of the soldered PCFSSs with different porosities depended on the higher-porosity section. After soldering the PCFSSs, Young’s modulus increased and the elongation at break reduced.

Enhanced Thermoelectric Cooling through Introduction of Material Anisotropy in Transverse Thermoelectric Composites.

Transverse thermoelectric materials can achieve appreciable cooling power with minimal space requirement. Among all types of material candidates for transverse thermoelectric applications, composite materials have the best cooling performance. In this study, anisotropic material properties were applied to the component phase of transverse thermoelectric composites. A mathematical model was established for predicting the performance of fibrous transverse thermoelectric composites with anisotropic components. The mathematical model was then validated by finite element analysis. The thermoelectric performance of three types of composites are presented, each with the same set of component materials. For each type of component, both anisotropic single-crystal and isotropic polycrystal material properties were applied. The results showed that the cooling capacity of the system was improved by introducing material anisotropy in the component phase of composite. The results also indicated that the orientation of the anisotropic component’s property axis, the anisotropic characteristic of a material, will significantly influence the thermoelectric performance of the composite. For a composite material consisting of Copper fiber and Bi2Te3 matrix, the maximum cooling capacity can vary as much as 50% at 300 K depending on the property axis alignment of Bi2Te3 in the composite. The composite with Copper and anisotropic SnSe single crystal had a 51% improvement in the maximum cooling capacity compared to the composite made of Copper and isotropic SnSe polycrystals.

Connected OFCity Challenge: Addressing the Digital Divide in the Developing World

Over the past 50 years, the development of information and communications technology has provided unprecedented support to the steady economic growth of developed countries. In recent years, some of the largest growth has been reported in emerging economies, which, however, often lack adequate telecommunications infrastructure to further sustain their development. Although a number of service providers and system vendors have started to address the issue, the challenges they encounter are substantially different from those in the developed world, including an unreliable electricity grid, poor fiber infrastructure, low revenue expectations, and often a harsh climate environment. This paper reports use cases and solutions pertinent to the development of the networking infrastructure in emerging economies, provided by organizations directly involved in such activities. After providing some background information on the current state of network infrastructure and the main challenges for Africa and rural China, the paper provides details on two proposed solutions. The first focuses on the provisioning of services and network infrastructure through the development of low-cost data centers, whereas the second proposes cost-effective adaptation of both fiber and hybrid copper–fiber technology to rural areas. The article is concluded with a brief discussion on the complementarity of the two approaches.

Experimental and simulation investigation of multi-tooth cutting process of long fiber using copper wire continuous feeding

To mass production of metal fibers with rough surface, a new type of multi-tooth tool and a special device were developed for fabrication process of metal fiber using continuous feeding of copper wire. A cutting model of multi-tooth tool was established. Whereafter, its cutting mechanism was discussed and analyzed by using a finite element method (FEM). The equivalent diameter and surface morphology of copper fiber which - were affected by processing parameters was investigated. Based on both experimental and simulation results, it is found that several fine tooth contacted with the copper wire could participate in the cutting process with continuous feeding of copper wire, a number of long copper fibers could be produced. Thus the processing efficiency of copper fiber with rough surface was greatly improved. In addition, the tool installation angle exhibited an influence on the equivalent diameter and surface morphology of copper fiber. Comparing with the feed rate, the equivalent diameter of copper fiber was remarkably affected by the cutting depth. However, these two parameters ha-d little effect on the surface morphology of copper fiber. Thus, the long copper fiber with rough surface could be fabricated under the condition of tool installation angle of 20–45°, wire feed rate of 0.42–0.72 m/s and cutting depth of 0.15–0.30 mm.

Characterization of mechanical properties and fracture mode of PLA and copper/PLA composite part manufactured by fused deposition modeling

In this paper, fused deposition modeling is used to process pure polylactic acid (PLA) and copper fiber reinforced PLA composite (Cu/PLA) specimen. Comparative experiments are performed on printed specimens of different raster angles (0°, 90°, 45°, 0°/90° and ± 45°, respectively). Tensile testing, dynamic mechanical analysis (DMA), and fracture surface analysis are employed to characterize all the specimens. The DMA exhibits remarkable improvement on storage modulus and loss tangent of Cu/PLA composite specimen. Due to the lower tensile strength and higher elasticity of Cu fiber compared with PLA, the tensile strength of Cu/PLA composite specimen decreases with the addition of Cu fiber, while the elongation-at-break increases. Both PLA and Cu/PLA specimens printed at a raster angle of 0° show highest tensile strength and dynamic mechanical properties, while the 90° raster angle with the lowest value. Fracture morphologies indicate that the failure of a specimen of 0° raster angle is intra-layer fracture, while inter-layer fracture occur in the specimen of 90° raster angle.

Porous copper fiber sintered felts with surface microchannels for methanol steam reforming microreactor for hydrogen production

In this study, a laser micro-milling technique was introduced into the fabrication process of surface microchannels with different geometries and dimensions on the porous copper fiber sintered felts (PCFSFs). The PCFSFs with surface microchannels as catalyst supports were then used to construct a new type of laminated methanol steam reforming microreactor for hydrogen production. The microstructure morphology, pressure drop, velocity and permeability of PCFSF with surface microchannels were studied. The effect of surface microchannel shape (rectangular, stepped, and polyline) and catalyst loading amount on the reaction performance of methanol steam reforming microreactor for hydrogen production was further investigated. Our results show that the PCFSF with rectangular microchannels demonstrated a lower pressure drop, higher average velocity and higher permeability compared to the stepped and polyline microchannel. Furthermore, the PCFSF with rectangular microchannels also exhibited the highest methanol conversion and H2 flow rate. The best reaction performance of methanol steam reforming microreactor for hydrogen production was obtained using PCFSF with rectangular microchannels when 0.5 g catalyst was loaded.

Performance Comparison Between Copper Cables and Fiber Optic in Data Transfer on Banjarmasin Weather Temperature Conditions

Copper wire cable and fiber optic cable are two communication media that are widely used in building data communication networks in today’s modern era. For network administrators, choosing the right type of cable to build a network is a must. Air temperature is one of the external factors that can affect the performance of network equipment. This paper provides a comparative analysis of the differences in performance between the use of fiber optic cables and copper wire cables which are capable of transferring data of 1 Gigabit per second. Performance measurement analysis includes the ability to transfer data from both media such as latency, throughput, and packet loss. For testing latency and throughput is done by sending as many as 65,000 data 30 times for each media. Whereas for packet loss testing is done by sending 10,000 data within 1 minute using test bandwidth on the Mikrotik router. From the test results, it can be seen that there is an effect of temperature changes on the performance of copper wire cable and fiber optic cable. The higher the air temperature, the packet loss, and latency will increase. As for the throughput value, the temperature only affects the throughput value on fiber optic cable and does not affect throughput on the copper wire cable.

Experimental studies on the compound thermo-hydraulic characteristics in a 3D inner finned tube with porous copper fiber inserts

A novel easy-to-manufacture porous copper fiber sintered cylinder insert (PCFSCI) is designed to enhance the convective heat transfer performance in a three-dimensional inner finned tube (3D-IFT). The compound heat transfer enhancement of the PCFSCI and 3D inner fins is investigated at the Reynolds number ranging from 3921 to 14,290. The results show that the combination of PCFSCI and 3D-IFT creates a synergistic effect and a maximum performance evaluation criterion (PEC) value of 2.29. Moreover, the effect of porosity, diameter and spacing of the PCFSCI on heat transfer performance is investigated. The results show that the Nusselt number and friction factor increase with the decrease of porosity. The PCFSCI with a diameter of 8 mm presents a better PEC than PCFSCI with diameters of 12 mm and 10 mm. The spacing has a slight effect on the PEC, but a great influence on the Nusselt number and friction factor. These phenomena can be attributed to the fluid mixing between the core flow and the flow in the annular region, as well as the local vortexes and the changing of velocity gradient produced in the annular region.

Highly Photoluminescent and Stable N-Doped Carbon Dots as Nanoprobes for Hg2+ Detection.

We developed a microreactor with porous copper fibers for synthesizing nitrogen-doped carbon dots (N-CDs) with a high stability and photoluminescence (PL) quantum yield (QY). By optimizing synthesis conditions, including the reaction temperature, flow rate, ethylenediamine dosage, and porosity of copper fibers, the N-CDs with a high PL QY of 73% were achieved. The PL QY of N-CDs was two times higher with copper fibers than without. The interrelations between the copper fibers with different porosities and the N-CDs were investigated using X-ray photoelectron spectroscopy (XPS) and Fourier Transform infrared spectroscopy (FTIR). The results demonstrate that the elemental contents and surface functional groups of N-CDs are significantly influenced by the porosity of copper fibers. The N-CDs can be used to effectively and selectively detect Hg2+ ions with a good linear response in the 0~50 μM Hg2+ ions concentration range, and the lowest limit of detection (LOD) is 2.54 nM, suggesting that the N-CDs have great potential for applications in the fields of environmental and hazard detection. Further studies reveal that the different d orbital energy levels of Hg2+ compared to those of other metal ions can affect the efficiency of electron transfer and thereby result in their different response in fluorescence quenching towards N-CDs.

Thermal or electrical bulk properties of rod-filled composites

The cell model (or self-consistent scheme) has been largely used to estimate the bulk thermal properties for dilute slender rods embedded in a matrix by applying a thermal gradient perpendicular to the main axis of the rod. This approach is then extended by considering a thermal gradient along the particle, or in other words a thermal flux through the end surfaces of the fiber. For a slender-body, this additional contribution is found to be negligible. Then, to circumvent the diluteness assumption, particle-particle contacts are considered when determining the effective thermal conductivity of the composite. This involves adding to the dilute result a new contribution depending on the magnitude of the Biot number (defined later) and on the micro-structures of the particles, and exhibiting a quadratic dependence on the particle concentration. Two assumed contact surface areas are investigating leading to the development of two micro-mechanical models, the difference being in the choice of the contact area. In addition, the model predictions are in good agreement with previously published data, where in-plane measurements of effective thermal conductivity are performed on highly conductive copper fibers impregnated with a poorly conductive PMMA matrix, for a wide range of fiber orientations and concentrations. When an appropriate cell size dimension for the dilute model is adopted, its predictions are also found to give an accurate fitting. Although this paper focuses on the thermal properties, the derivation can be carried over to the electrical properties with very minor modifications. This has been carried out for estimating the effective electrical conductivity of several CNTs (i.e., SWCNT and MWCNT) embedded in an epoxy matrix, leading again to good agreements.

Thermal Conductivity Measurements of Novel Porous Copper Fiber Sintered Sheet

In this work, a porous copper fiber sintered sheet (PCFSS) is fabricated by using a low-temperature solid-phase sintering method. Copper fiber is a raw material that is produced by a cutting method with a multi-tooth tool. A novel reference plate method (RPM) with a steady state heat transfer process is introduced to measure the thermal conductivity of PCFSS. The study involves experimentally investigating the effects of reference plate materials as well as the porosity and porosity gradients of PCFSS on thermal conductivity. The findings indicate that reasonable measurement results of thermal conductivity of PCFSS are obtained when 304 stainless steel is selected as a reference plate material when compared with that in the case of a red copper plate. The thermal conductivity increases with a decrease in the porosities of PCFSS in the approximate range of 70%–90%. With respect to the approximate measuring temperature range of 34°C~58°C, the thermal conductivities of PCFSSs with 70%, 80% and 90% porosities correspond to 25.35 W/(m·°C), 15.01 W/(m·°C) and 11.24 W/(m·°C), respectively. The thermal conductivity of PCFSS with 70%-80%-90% gradient porosity corresponds to 13.43 W/(m·°C), and this value is between 80% and 90% porosity of PCFSS.

Methanol steam reforming performance optimisation of cylindrical microreactor for hydrogen production utilising error backpropagation and genetic algorithm

To optimise methanol steam reforming performance of cylindrical microreactor for hydrogen production, an error backpropagation algorithm was used to build a mathematical model for reaction performance of different microreactors for hydrogen production. Additionally, a genetic algorithm (GA) was utilised to process the computational model to obtain the optimum reaction parameters. The reliability of optimum reaction parameters of cylindrical microreactor for hydrogen production was verified by experiments. Firstly, take platemicroreactor as an example, the porosity of porous copper fiber sintered sheet (PCFSS), reaction temperature of methanol steam reforming for hydrogen production, injection velocity of the methanol and water mixture, and catalyst loading of PCFSS were considered as input data, whereas methanol conversion was used as output data. The computational model for specific testing system was gained by utilising input and output data from specific testing system to train the mathematical model for different microreactors, combining with matrix laboratory (MATLAB) neural network toolbox and designed MATLAB program. The Emax of 5% for plate microreactor and Emax of 3.2% for cylindrical microreactor verified the good predictive ability and reliability of the computational model for plate and cylindrical microreactor, indicating the reliability and universal applicability of the mathematical model for different microreactors. Secondly, the effects and mechanisms of PPI, reaction temperature, injection velocity, and catalyst loading on methanol conversion were studied, relying on the computational model. Finally, the optimum reaction parameters were acquired using GA, MATLAB neural network toolbox and designed MATLAB program. The validity of the optimum reaction parameters of cylindrical microreactor for hydrogen production was confirmed by experiments. This study provides a feasible method for methanol steam reforming performance optimisation for hydrogen production.

High ampacity of superhelix graphene/copper nanocomposite wires by a synergistic growth-twisting-drawing strategy

Nanocarbon materials can provide effective reinforcement to a surrounding composite matrix. However, the fabrication of nanocarbon/metal composites with superior comprehensive properties remains challenging. Here, we developed a simple cyclic growth-twisting-drawing method to fabricate superhelix graphene/copper nanocomposite wires composed of massive, strongly bonded, and super-helically arranged fine copper fibers with interfacial graphene layers. The obtained nanocomposite wires with a small graphene volume fraction of ∼0.32% exhibit a largely improved current carrying capacity of 5.8 × 1010 A m−2, ∼2.6 times of that of pure copper wires. Furthermore, the electrical conductivity, 5.01 × 107 S m−1, is comparable to that of pure copper. These nanocomposite wires also exhibit improved strength and ductility, 10% and 80% increases compared with that of pure copper wires. These multiple enhanced properties can be attributed to the microscopic superhelix structure with the interfacial graphene layers embedded in the entire multi-level structure. With their largely improved current carrying capacity and mechanical reinforcement, these highly electrically conductive nanocomposite wires promise widely potential applications in the areas of heavy duty, high power electronics and electricity transmission.

Development of micellar solid-phase microextraction fiber based on CTAB-templated mesoporous silica electrochemically assisted self-assembled on wire: Application to chromatographic determination of polycyclic aromatic hydrocarbons

ABSTRACTThis paper describes the development of a new micellar solid-phase microextraction fiber based on cetyltrimethylammonium bromide-templated mesoporous silica electrochemically assisted self-assembled on copper wire for sensitive determination of polycyclic aromatic hydrocarbons by HPLC. After optimization of experimental parameters, non-polar analytes of PAHs were successfully determined in water samples after microextraction by CTAB/MCM-41 copper fiber as micellar organic platform. The proposed method indicated good linearity in the range 0.01–82.5 µg L−1 and limits of detection in the range 3–46 ng L−1. Relative standard deviations of the method were obtained in the range 3.1–8.3%.

Al₂O₃-Cu Substrate with Co-Continuous Phases Made by Powder Sintering Process.

Ceramic-Al substrates with co-continuous ceramic and metal phases, which exhibit high thermal conductivity and compatible coefficient of thermal expansion (CTE), have been widely investigated through the process of die-casting. In this research, a kind of powder sintering process was proposed for fabricating ceramic-Cu composite substrates with co-continuous phases. Copper fiber (Cuf) has excellent thermal conductivity and large aspect ratio, making it an ideal material to form bridging network structures in the ceramic-Cu composite. To maintain the large aspect ratio of Cuf, and densify the composite substrate, ZnO-SiO2-CaO glass was introduced as a sintering additive. Both Al2O3/glass/Cuf and Al2O3/30glass/Cup composite substrates were hot-pressed at 850 °C under 25 MPa. Experimental results showed that the thermal conductivity of Al2O3/30glass/30Cuf composite substrate was as high as 38.9 W/mK, which was about 6 times that of Al2O3/30glass; in contrast, the thermal conductivity of Al2O3/30glass/30Cup composite substrate was only 25.9 W/mK. Microstructure observation showed that, influenced by hot press and corrosion of molten ZnO-SiO2-CaO glass, the copper fibers were deformed under hot-pressing, and some local melting-like phenomena occurred on the surface of copper fiber at 850 °C under 25 MPa. The molten phase originating from surface of Cuf welded the overlapping node of copper fibers during cooling process. Finally, the interconnecting metal bridging in ceramic matrix was formed and behaved as a rapid heat-dissipating channel, which is similar to substrates prepared through die-casting process by porous ceramic and melted Al.

Noise characterization of IUCAA digital sampling array controller

IUCAA Digital Sampling Array Controller (IDSAC) is a flexible and generic yet powerful CCD controller which can handle a wide range of scientific detectors. Based on an easily scalable modular backplane architecture consisting of Single Board Controllers (SBC), IDSAC can control large detector arrays and mosaics. Each of the SBCs offers the full functionality required to control a CCD independently. The SBCs can be cold swapped without the need to reconfigure them. Each SBC can handle data from up to four video channels with or without dummy outputs at speeds up to 500 kilo Pixels Per Second (kPPS) Per Channel with a resolution of 16 bits. Communication with Linux based host computer is through a USB3.0 interface, with the option of using copper or optical fibers. A Field Programmable Gate Array (FPGA) is used as the master controller in each SBC which allows great flexibility in optimizing performance by adjusting gain, timing signals, bias levels, etc. using user-editable configuration files without altering the circuit topology. Elimination of thermal kTC noise is achieved via Digital Correlated Double Sampling (DCDS). We present the results of noise performance characterization of IDSAC through simulation, theoretical modeling, and actual measurements. The contribution of different types of noise sources is modeled using a tool to predict noise of a generic DCDS signal chain analytically. The analytical model predicts the net input referenced noise of the signal chain to be 5 electrons for 200k pixels per second per channel readout rate with 3 samples per pixel. Using a cryogenic test set up in the lab, the noise is measured to be 5.4 e (24.3 \muV), for the same readout configuration.

Laser sintering and laser parameters optimization for porous foam microchannel reactor

Porous foam microchannel reactor can effectively improve the reaction efficiency of Methanol reforming hydrogen production. Currently, porous foam microchannel reactors are primarily formed by the solid phase and liquid phase sintering techniques which generally require the metal fiber sheet of semi-finished products sinter at 800-1000℃ temperature conditions for 30–60 minutes. In this paper, a method of laser-sintered porous metal fiber sintering plate is proposed. Compared with the traditional methods, laser sintering technology has the advantages of shorter sintering time and retaining the surface microstructure which is more conducive to the adhesion of the catalyst. The effects of laser power, scanning rate, scanning distance, and scanning path on the sintering effect were also studied and analyzed. The results show that the porosity of copper fiber laser sintering sheets can reach 80% by laser sintering. When the laser sintering parameters for I=60A, f=20Hz, h=6.5ms, v=15mm/s, under the condition of variable speed sintering can achieve the best mechanical properties.